JP4962559B2 - Anti-reflection coating composition - Google Patents

Abstract

To provide an antireflection coating composition having a low surface tension and excellent coating properties and capable of forming an antireflection film with a low refractive index, without use of PFOS nor PFOA having 7 or more carbon atoms. An antireflection coating composition which contains a fluorinated surfactant (A) containing a compound (A1) represented by the following formula (I), a water-soluble polymer (B) and an aqueous medium (C): €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒR 1 -O-(R 2 -O) n -R 3 -X 1 €ƒ€ƒ€ƒ€ƒ€ƒ(I) wherein R 1 is a linear or branched perfluoroalkyl group of which the terminal fluorine atom may be substituted by a hydrogen atom or a chlorine atom, each of R 2 and R 3 which are independent of each other, is a linear or branched perfluoroalkylene group, provided that the total number of carbon atoms in R 1 , R 2 and R 3 is at most 5, n is 0 or an integer of at least 1, X 1 is -COOH or -C(CF 2 Z 1 )(CF 2 Z 2 )OH, which may form a salt, and each of Z 1 and Z 2 is a hydrogen atom, a fluorine atom, a chlorine atom or a trifluoromethyl group.

Description

  The present invention relates to an antireflection coating composition.

When forming a photoresist pattern by photolithography, if light reflected from the boundary surface between the photoresist layer and the substrate and the surface of the photoresist layer interferes during exposure, the dimensional accuracy of the pattern is reduced. In order to reduce the reflected light, a method of forming an antireflection film on the surface of the photoresist layer has been studied. The antireflection performance of this antireflection film is determined by the refractive index and film thickness of the antireflection film at the wavelength of the target light source, and the refractive index and film thickness of the photoresist layer. The refractive index needs to be lower than the refractive index of the photoresist layer.
In general, a composition for forming an antireflection film has (a) a surfactant, (b) a water-soluble binder polymer, and (c) an aqueous medium as main constituent components. Then, (a) the refractive index of a film | membrane is reduced by using the compound containing a fluorine atom as surfactant.

  However, in recent years, there have been concerns about the environmental impact of PFAS (Perfluoroalkyl sulfates) and PFAA (Perfluoroalkyl Acids) having 7 or more carbon atoms, which have been used in conventional antireflection coating compositions. For example, the United States EPA (Environment) Protection Agency's SNUR (Significant New Use Rule, dated March 11, 2002, etc.) and others are also trying to set restrictions when importing and manufacturing. Under such circumstances, there is a strong demand for a composition for an antireflection film that does not use PFAS and PFAA having 7 or more carbon atoms.

Under such circumstances, for example, Patent Documents 4 to 7 below propose a coating composition for an antireflection film using (b) a polymer containing a fluorine atom as a water-soluble binder polymer.
JP-A-5-188598 JP 7-160002 A JP-A-8-305032 JP-A-8-44066 JP-A-9-325500 Japanese Patent Laid-Open No. 11-124531 JP 2004-37887 A

However, in the conventional coating compositions as described in Patent Documents 4 to 7, it is possible to use PFAS and PFAA having 7 or more carbon atoms or a hydrocarbon-based surfactant as the surfactant. Are listed. Since the anti-reflective coating composition is applied onto a resist film having a low surface tension, it is coated with a considerable amount of (a) a surfactant, particularly when (c) water is used as an aqueous medium. It is necessary to reduce the surface tension of the composition. However, hydrocarbon-based surfactants do not necessarily have sufficient surface tension reducing ability, so it is necessary to add them in large amounts, and since the refractive index of the hydrocarbon-based surfactants themselves is relatively high, There is a problem that the refractive index is hardly lowered.
Patent Document 5 includes perfluorobutanesulfonic acid and perfluorobutanoic acid as water-soluble fluorine compounds contained in the composition. However, it is unclear whether the antireflection film obtained using these compounds has a uniform film thickness and a sufficiently low refractive index.
The present invention has been made in view of the above circumstances, and without using PFAS and PFAA having 7 or more carbon atoms, the surface tension is low, the coatability is excellent, and an antireflection film having a low refractive index can be formed. An object is to provide a coating composition.

（式中、Ｙ ^１ 、Ｙ ^２ はそれぞれ独立に水素原子、フッ素原子または塩素原子を示し、Ｙ ^３ は水素原子、フッ素原子、塩素原子、メチル基またはトリフルオロメチル基を示し、Ｑはエーテル結合またはエステル結合を示し、Ｒ ^５ 、Ｒ ^６ 及びＲ ^７ はそれぞれ独立に、炭素数６以下の、直鎖状または分岐状のパーフルオロアルキレン基を示し、Ｘ ^３ は塩を形成していてもよい酸性ＯＨ基を有する官能基を示し、ａ、ｂはそれぞれ独立に０または1以上の整数を示す。）
In order to solve the above problems, an antireflection coating composition of the present invention comprises a fluorine-containing surfactant (A) containing a compound (A1) represented by the following general formula (I), a water-soluble polymer (B), Containing an aqueous medium (C) ,
The water-soluble polymer (B) contains 50% by mass or more of a water-soluble fluoropolymer (B1) having a polymerization unit (b1) represented by the following general formula (IV) .
R ¹ —O— (R ² —O) _n —R ³ —X ¹ (I)
(In the formula, R ¹ represents a linear or branched perfluoroalkyl group in which the terminal fluorine atom may be substituted with a hydrogen atom or a chlorine atom, and R ² and R ³ are each independently Represents a chain or branched perfluoroalkylene group, the total number of carbon atoms of R ¹ , R ² and R ³ is 5 or less, n represents 0 or an integer of 1 or more, and X ¹ forms a salt. And —COOH or —C (CF ₂ Z ¹ ) (CF ₂ Z ² ) OH, each of Z ¹ and Z ² is a hydrogen atom, a fluorine atom, a chlorine atom or a trifluoromethyl group. )

Wherein Y ¹ and Y ² each independently represent a hydrogen atom, a fluorine atom or a chlorine atom, Y ³ represents a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group or a trifluoromethyl group, and Q represents an ether bond Or an ester bond, R ⁵ , R ⁶ and R ⁷ each independently represents a linear or branched perfluoroalkylene group having 6 or less carbon atoms, and X ³ may form a salt. A functional group having an acidic OH group, a and b each independently represent 0 or an integer of 1 or more.)

  According to the present invention, without using PFAS and PFAA having 7 or more carbon atoms, which may be prohibited from the viewpoint of environmental impact, the surface tension is low, the coatability is excellent, and the refractive index is low. An antireflection coating composition capable of forming an antireflection film can be realized.

<Fluorine-containing surfactant (A)>
The fluorine-containing surfactant (A) used in the present invention (hereinafter sometimes simply referred to as component (A)) contains the compound (A1) represented by the general formula (I).
The perfluoroalkyl group in the present specification means a group in which all of the hydrogen atoms bonded to the carbon atoms of the alkyl group are substituted with fluorine atoms, and the ether bond-containing perfluoroalkyl group is a perfluoroalkyl group. A group in which an etheric oxygen atom is inserted into the carbon chain.
The alkyl group in the perfluoroalkyl group may be linear or branched. The terminal fluorine atom of the perfluoroalkyl group may be substituted with a hydrogen atom or a chlorine atom.
The carbon chain having an etheric oxygen atom in the ether bond-containing perfluoroalkyl group may be linear or branched.
In the component (A), the fluorine-containing alkyl group present in the molecule has 5 or less carbon atoms. That is, the component (A) has neither a perfluoroalkyl group having 6 or more carbon atoms nor an ether bond-containing perfluoroalkyl group having 6 or more carbon atoms. The lower limit of the number of carbon atoms of the fluorine-containing alkyl group is not particularly limited, but is preferably 4 or more from the viewpoint of surface tension reducing ability. The number of carbon atoms is more preferably 4 or 5.

The compound (A1) has —COOH or —C (CF ₂ Z ¹ ) (CF ₂ Z ² ) OH. Z ¹ and Z ² are each H, F, Cl, or CF ₃ .
In the component (A), the —OH group of —COOH and —C (CF ₂ Z ¹ ) (CF ₂ Z ² ) OH may form a salt. Specifically acidic OH group may be a -OA ² to form a salt.
A ² represents an alkali metal, NH ₄ , a monovalent group derived from an organic amine, or a quaternary ammonium group. Examples of the alkali metal include lithium, sodium, and potassium. Among these, A ² is more preferably a monovalent group derived from an organic amine or a quaternary ammonium group.

[Compound (A1)]
In the compound (A1) represented by the general formula (I), “R ¹ —O— (R ² —O) _n —R ³ —” corresponds to “an ether bond-containing perfluoroalkyl group”.
In the general formula (I), R ¹ is a perfluoroalkyl group, which may be linear or branched. In R ¹ , the terminal fluorine atom may be substituted with a hydrogen atom or a chlorine atom. _C 4 _F 9 as _{^{R 1 -, C 3 F 7}} -, C 2 F 5 -, CF 3 - are _{preferred, C 2 F 5, C 3} F 7 is preferred.
R ² and R ³ are each independently a linear or branched perfluoroalkylene group. R ² is _{-CF 2 CF 2 -, - CF} 2 CF (CF 3) - are preferred, ^{R 3} is _{-CF 2 CF 2 -, - CF} 2 - are preferred.
The total number of carbon atoms of R ¹ , R ² and R ³ is 5 or less, preferably 2 to 5, and more preferably 4 or 5. However, when X ¹ in the general formula (I) is —C (CF ₂ Z ¹ ) (CF ₂ Z ² ) OH, the total number of carbon atoms of R ¹ , R ² and R ³ is 4 or 5. preferable.
N in the general formula (I) is 0 or an integer of 1 or more, preferably 0 or an integer of 1 to 3, more preferably 0, 1 or 2.
Since the compound (A1) is excellent in water solubility, the composition for antireflection coating containing it is in a uniform mixed state. Therefore, the obtained antireflection film also has a uniform composition and a uniform film thickness. Further, the compound (A1) has an advantage that it is dissolved to some extent in water even when it is not salified with an alkali. An important characteristic of the antireflection film is matching of acidity with the underlying resist. If the acidity of the antireflective film is too high, the acid component on the antireflective film will penetrate into the resist layer, reducing the excessive film, making the pattern round-topped (the rectangular head is excessively developed and scraped off) Will be rounded.) On the other hand, if the acidity is too low, the acid component of the resist layer moves to the antireflection film, and the pattern becomes T-topped (the development of the rectangular head portion is insufficient and the portion to be removed remains). Invite.
When the compound (A1) is used, it is not always necessary to use it by chlorination. Therefore, it is easy to adjust the acidity of the antireflection film, and it can be used for coating various resist layers.

Preferred examples of compound (A1) include compound (A11) represented by the following general formula (III).
M ¹ CF ₂ CF ₂ O (CF ₂ CF ₂ O) _p CF ₂ COOA ¹ (III)
(In the formula, M ¹ represents a fluorine atom, a hydrogen atom or a chlorine atom, A ¹ represents a hydrogen atom, an alkali metal, NH ₄ , a monovalent group derived from an organic amine, or a quaternary ammonium group; Is 0 or 1.)
In the general formula (III), M ¹ is a fluorine atom, a hydrogen atom or a chlorine atom, preferably a fluorine atom.
A monovalent group derived from an alkali metal, NH ₄ , or organic amine as A ¹ , or a quaternary ammonium group is the same as A ² above, including preferred embodiments. A ¹ is preferably a hydrogen atom.
p is 0 or 1, preferably 1.
In the composition for antireflection coating of the present invention, it is preferable to use the compound (A11) represented by the general formula (III) as the fluorine-containing surfactant (A).

In the composition for antireflection coating of the present invention, the fluorine-containing surfactant (A) may be used alone or in combination of two or more.
The amount of the fluorine-containing surfactant (A) used is preferably set so that the surface tension of the antireflection coating composition falls within a desired range. The preferred range of the surface tension of the antireflection coating composition depends on the coating method, but in any coating method, good coating properties can be obtained whether the surface tension of the antireflection coating composition is too high or too low. I can't get it.
For example, the content of the fluorine-containing surfactant (A) in the antireflection coating composition is preferably in the range of 0.001 to 10% by mass, more preferably 0.05 to 5% by mass, and 0.1 to 1% by mass. % Is more preferable.

<Water-soluble polymer (B)>
[Water-soluble fluoropolymer (B1)]
[Polymerized unit (b1)]
As the water-soluble polymer (B) (hereinafter sometimes simply referred to as the component (B)), a known water-soluble polymer can be used as a film forming component of the antireflection film.
As the component (B), a water-soluble fluoropolymer (B1) having a polymer unit (b1) represented by the following general formula (IV) is preferable.

Wherein Y ¹ and Y ² each independently represent a hydrogen atom, a fluorine atom or a chlorine atom, Y ³ represents a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group or a trifluoromethyl group, and Q represents an ether bond Or an ester bond, R ⁵ , R ⁶ and R ⁷ each independently represents a linear or branched perfluoroalkylene group having 6 or less carbon atoms, and X ³ may be an acid which may form a salt. A functional group having an OH group, a and b each independently represent 0 or an integer of 1 or more.)

In the general formula (IV), Y ¹ and Y ² each independently represent a hydrogen atom, a fluorine atom or a chlorine atom. Preferably both Y ¹ and Y ² are fluorine atoms.
Y ³ represents a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group or a trifluoromethyl group, preferably a fluorine atom.
Q represents an ether bond or an ester bond, and preferably an ether bond.
R ⁵ , R ⁶ and R ⁷ each independently represents a linear or branched perfluoroalkylene group having 6 or less carbon atoms. R ^5, the number of carbon atoms of ^{R 6} and ^{R 7} are 1 to 3 each preferably 2 or 3 is more preferable. Preferable examples of R ⁵ , R ⁶ and R ⁷ include —C ₂ F ₄ —, —C ₃ F ₆ —, —CF ₂ —CF (CF ₃ ) — and the like.
a and b each independently represent an integer of 0 or 1 or more. a and b are each preferably an integer of 0 or 1-3. It is preferable that the sum of a and b is 0 or 1-3.

In the general formula (IV), X ³ represents a functional group having an acidic OH group. As the functional group having an acidic OH group, —COOH, —SO ₃ H, —OP (═O) (OH) ₂ , or —C (CF ₂ Z ¹ ) (CF ₂ Z ² ) OH is preferable. Z ¹ and Z ² are each H, F, Cl, or CF ₃ . In particular, —COOH, —SO ₃ H, and —C (CF ₂ Z ¹ ) (CF ₂ Z ² ) OH are preferable. X ³ may form a salt, but preferably does not form a salt.

  As the polymer unit (b1) represented by the general formula (IV), a polymer unit (b11) represented by the following general formula (VI) is preferable.

_{-CF 2 CF [O (CF 2} CF (CF 3) O) s (CF 2) t X 4] - ... (VI)
(In the formula, s represents an integer of 0 to 5, t represents an integer of 1 to 5, and X ⁴ represents —COOH, —SO ₃ H, or —C (CF ₂ Z ¹ ) (CF ₂ Z ² ). OH represents Z ¹ and Z ² are each H, F, Cl or CF ₃ )
As the fluorine-containing monomer forming the polymerized unit (b11),
CF ₂ = CF [O (CF ₂ CF (CF ₃ ) O) _{s ′} (CF ₂ ) _{t ′} X ^{4 ′} ] is preferred.
In the monomer, s ′ is preferably an integer of 0 to 3, and t ′ is preferably 1 to 3. X ^{4 ′} is the same group as X ⁴ in formula (VI), or a group that becomes X ⁴ through a hydrolysis reaction.

Preferable examples of the polymer unit (b11) represented by the general formula (VI) include the following polymer units.
_{- [CF 2 CF (OCF 2} CF 2 CF 2 COOH)] -,
_{- [CF 2 CF (OCF 2} CF (CF 3) OCF 2 CF 2 COOH)] -,
_{- [CF 2 CF (OCF 2} CF (CF 3) OCF 2 CF 2 CF 2 COOH)] -,
_{- [CF 2 CF (OCF 2} CF 2 CF 2 OCF 2 CF 2 COOH)] -,
_{- [CF 2 CF (OCF 2} CF (CF 3) OCF 2 CF 2 SO 3 H)] -.

  In the present invention, the proportion of the polymerized units (b1) in the total polymerized units constituting the water-soluble fluoropolymer (B1) is preferably 20 mol% or more, more preferably 60 mol% or more, and 100 mass%. But you can. If it is less than the lower limit of the above range, the water solubility of the fluoropolymer will decrease.

[Polymerized unit (b2)]
The water-soluble fluoropolymer (B1) may have a polymer unit other than the polymer unit (b1). For example, you may have the polymerization unit (b2) represented by the following general formula (VII).
_{-CF 2 CF [(CF 2)} u X 5] - ... (VII)
(In the formula, u represents an integer of 1 to 10, X ⁵ represents —COOH, —SO ₃ H, or —C (CF ₂ Z ¹ ) (CF ₂ Z ² ) OH, and Z ¹ and Z ² represent H, F, Cl or CF ₃ respectively.)
As the fluorine-containing monomer forming the polymerized unit (b2), CF ₂ ═CF [(CF ₂ ) _{u ′} X ^{5 ′} ] is preferable. In the monomer, u ′ is preferably 1 to 5. X ^{5 ′} is the same group as X ⁵ in formula (VII), or a group that becomes X ⁵ through a hydrolysis reaction.

[Polymerized unit (b3)]
The water-soluble fluorine-containing polymer (B1) may have a polymer unit (b3) whose main chain is the same as the polymer unit (b1) and is not included in the polymer units (b1) and (b2). .
As the polymerization unit (b3), for example, a polymerization unit formed by cleavage of a double bond of the following fluorine-containing monomer is preferable.
CF ₂ = CF ₂ ,
CF ₂ = CFCF ₃ ,
CF ₂ = CF (CF ₂ ) _k CF ₃
CF ₂ = CH ₂ ,
CF ₃ CH═CH (CF ₂ ) _k CF ₃ ,
_{CH 2 = CH [(CF 2} ) k CF 3],
_{CH 2 = CHCH 2 (CF 2} ) k CF 3
CF ₂ = CF [O (CF ₂ ) _k CF ₃ ],
CF ₂ = CF [O [CF ₂ CF (CF ₃ ) O] ₁ CF ₂ CF ₂ CF ₃ ] and the like.
In the above, k represents an integer of 1 to 10, and l represents an integer of 1 to 3. Among these, CF ₂ = CF ₂ , CF ₂ = CFCF _{3 and the} like are particularly preferable.

[Polymerized unit (b4)]
The water-soluble fluoropolymer (B1) may contain a polymer unit (b4) having an etheric oxygen atom in the main chain. As the polymerized unit (b4), the following polymerized units are preferable.
_{-CF 2 CF (CF 3) O-} ,
_{- (CF 2) k 'O-} ,
In the above, k ′ represents an integer of 1 to 3.

  The mass average molecular weight of the water-soluble fluoropolymer (B1) (converted to PMMA by gel permeation chromatography method, the same shall apply hereinafter) is preferably 50,000 or less and more preferably 30,000 or less because good water solubility is obtained. preferable. The mass average molecular weight is preferably 1,000 or more from the viewpoint of obtaining good film-forming properties.

Although there is no limitation in particular as a manufacturing method of a water-soluble fluorine-containing polymer (B1), the following method (i) or method (ii) is mentioned preferably.
(I) A method of polymerizing a fluorine-containing monomer having a precursor functional group that can be converted into “functional group having acidic OH group”, and then converting the precursor functional group to “functional group having acidic OH group”.
(Ii) A method of introducing a “functional group having an acidic OH group” into a part of the polymer after polymerizing the fluorine-containing monomer.
Examples of methods _{(i), CF 2 = CF} [O (CF 2 CF (CF 3) O) s '(CF 2) t' COOCH 3] (s ', t' are as defined above. ), Followed by hydrolysis of the —COOCH ₃ moiety, CF ₂ ═CF [O (CF ₂ CF (CF ₃ ) O) _{s ′} (CF ₂ ) _{t ′} SO ₂ F] (s ′, t ′ Represents the same meaning as described above), and a method of hydrolyzing the —SO ₂ F moiety after polymerization is preferred.
The polymerization method is not particularly limited, but a polymerization reaction in which a polymerization initiator is added to the fluorine-containing monomer and heated is preferable.

As the polymerization initiator, peroxides, azo compounds and the like are preferable.
Preferred examples of the peroxide include peroxyketals, diacyl peroxides, peroxycarbonates, peroxyesters, ammonium persulfate, and potassium persulfate.
Preferred examples of the azo compound include azonitriles, azoamides, cyclic azoamides, azoamidines, and the like.
It is preferable that the usage-amount of a polymerization initiator is 0.01-10 mol% with respect to the total number of moles of the monomer used for a polymerization reaction.
In the polymerization reaction, a chain transfer agent may be used. The amount of the chain transfer agent used for the polymerization reaction is preferably 0.01 to 10 mol% based on the total number of moles of monomers.
In the polymerization reaction, a medium may or may not be used. When used, the polymerization reaction is preferably performed in a state where the fluorine-containing monomer is dissolved or dispersed in the medium. As the medium, water, a fluorine-containing solvent or the like is preferably used.

[Other water-soluble polymer (B2)]
As the water-soluble polymer (B) contained in the composition for antireflection coating of the present invention, other water-soluble polymer (B2) not containing fluorine may be used.
As the other water-soluble polymer (B2), a known water-soluble polymer can be appropriately used. Specific examples include polyvinyl pyrrolidone, polyacrylic acid, polyvinyl alcohol, water-soluble polysiloxane, polysaccharides and the like. These may be used alone or in combination of two or more.

The water-soluble polymer (B) contained in the composition for antireflection coating of the present invention may be a water-soluble fluoropolymer (B1), another water-soluble polymer (B2), or a combination of both. . In order to improve the film-forming property using at least the water-soluble fluoropolymer (B1), it is preferable to use another water-soluble polymer (B2) in combination as necessary.
In the water-soluble polymer (B) contained in the antireflection coating composition of the present invention, the proportion of the water-soluble fluoropolymer (B1) is preferably 50% by mass or more, more preferably 70% by mass or more, and 100 It may be mass%. If it is less than the lower limit of the above range, the effect of reducing the refractive index is lowered.
The content of the water-soluble polymer (B) in the antireflective coating composition of the present invention may be within a range in which the component (B) can be dissolved and a film having a desired thickness can be formed during coating. Specifically, 0.1-20 mass% is preferable, 1-10 mass% is more preferable, and 3-7 mass% is further more preferable.

<Aqueous medium (C)>
The aqueous medium (C) is preferably selected from water and a water-soluble organic solvent. Water is preferable, and a water-soluble organic solvent and water may be used in combination.
The water is preferably water from which organic impurities, metal ions and the like have been removed by treatments such as distillation, ion exchange treatment, filter treatment, and various adsorption treatments.
The water-soluble organic solvent is not particularly limited as long as it is an organic solvent that dissolves 0.1% by mass or more with respect to water, and examples thereof include methyl alcohol, ethyl alcohol, isopropyl alcohol, 2-butanol, and hexylene glycol. Alcohols; ketones such as acetone and methyl ethyl ketone; esters such as methyl acetate, ethyl acetate and ethyl lactate; dimethylformamide, dimethyl sulfoxide, methyl cellosolve, cellosolve, butyl cellosolve, cellosolve acetate, alkyl cellosolve acetate, butyl carbitol, carbitol Examples include polar solvents such as acetate. Of these, alcohols are preferred.
The content of the aqueous medium (C) in the composition for antireflective coating of the present invention may include (A) component, (B) component, and other necessary components added as necessary. And is set so that all components are dissolved. 70-99.9 mass% is preferable, for example, and, as for content of an aqueous medium (C), 95-99 mass% is more preferable.

<Organic amine (D)>
If necessary, the composition for antireflection coating of the present invention can contain an organic amine (D). By adding the organic amine (D) and adjusting the pH of the composition for antireflection coating, intermixing with the photoresist layer can be suppressed.
Specific examples of the organic amine (D) include NH ₃ , tetramethylammonium hydroxide (N (CH ₃ ) ₄ OH), trimethyl-2-hydroxyethylammonium hydroxide, alkanolamine, alkylamine, and aromatic amine. It is done.
The content of the organic amine (D) in the antireflection coating composition can be set so that the pH of the antireflection coating composition is in a range suitable for forming a resist pattern. For example, it is preferably within the range of 50 to 95% by mass of the total amount of acidic functional groups.

<Other additives>
The antireflection coating composition of the present invention can contain various additives as required. For example, a known surfactant not included in the component (A) may be added for the purpose of improving the wettability and leveling property to the photoresist layer.
Examples of the surfactant include a compound having a polyfluoroalkyl group and a polyoxyethylene group (manufactured by 3M, product names: Florard “FC-430”, “FC-4430”, etc.), acetylene glycol and polyoxyethylene. Added compounds (product names: “Surfinol 104”, “Surfinol 420”), alkyl sulfonic acids and alkyl benzene sulfonic acids (for example, Nikko Chemicals, product name: Nikkor “SBL-2N-” manufactured by Air Products) 27 ”and the like, and a compound containing a hydroxyl group and not containing a polyoxyethylene group (polyglycerin fatty acid ester, etc.) are preferred.

<Application>
The composition for antireflection coating of the present invention is suitable as a coating solution for forming an antireflection film for photoresist. Specifically, when forming a pattern by photolithography using a photoresist, it is suitable as a coating solution for forming an antireflection film provided on the surface of the photoresist layer. There is no restriction | limiting about a photoresist layer, It can apply to each photoresist for excimer lasers, such as for g line | wire, i line | wire, KrF, and ArF.

<Method for forming antireflection film>
The antireflection coating composition of the present invention is applied to the surface on which the antireflection film is to be formed to form a coating film, and then the solvent in the coating film is removed to form the antireflection film. Can do. As the coating method, the spin coat method is preferred because of excellent uniformity and simplicity of the coating film. After forming a coating film, you may heat-dry using a hotplate, oven, etc. as needed. For example, in the case of a hot plate, the drying conditions are preferably 70 to 100 ° C. and 30 to 180 seconds.
When the antireflection film is intended to prevent reflection at the time of exposure in the photolithography process, the thickness of the antireflection film may be set by a known antireflection theory. Specifically, an odd multiple of “(exposure wavelength) / (4 × refractive index of antireflection film)” is preferable because of excellent antireflection performance.

The antireflection coating composition of the present invention is excellent in effectively reducing the surface tension by adding the above-mentioned fluorine-containing surfactant (A) to the water-soluble polymer (B) and the aqueous medium (C). Application performance can be realized. Further, as shown in the examples described later, the fluorine-containing surfactant (A) has a higher effect of lowering the surface tension as compared with the conventional surfactant, so that a good coating performance can be obtained with a relatively small amount of addition. Can be achieved. Further, since the fluorine-containing surfactant (A) itself contains fluorine, the refractive index is low, and the refractive index of the antireflection film is obtained by adding the fluorine-containing surfactant (A) to the composition for antireflection coating. Is prevented from increasing. Furthermore, since the fluorine-containing surfactant (A) has an acidic OH group similar to that of the fluorine-containing polymer, a phenomenon such as aggregation due to the action of functional groups hardly occurs, and the composition solution has excellent storage stability.
Therefore, according to the present invention, it is possible to use a coating solution without deteriorating the refractive index of the composition without using a compound such as PFAS having 7 or more carbon atoms, which may be prohibited from use due to the problem of environmental impact. A coating composition having a high coating performance can be obtained by reducing the surface tension.

  In particular, when the water-soluble fluoropolymer (B1) is used as the water-soluble polymer (B), since the polymer (B1) contains fluorine, it has a low refractive index and forms an antireflection film having a low refractive index. In addition, it is preferable. Further, since the polymer (B1) has an acidic OH group, the antireflection film has excellent water solubility. Therefore, since it is easy to dissolve in the developer used in the photolithography process, the antireflection film is easily removed in the development process.

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.
(Production Example 1: Synthesis of water-soluble fluoropolymer (B1))
By the method (i), a polymer (B1) composed of the polymer unit (b11) represented by the general formula (VI) was produced.
That is, after replacing the air in the system of the 1.3 L autoclave with a stirrer with nitrogen, 1.18 kg of CF ₂ = CFOCF ₂ CF ₂ CF ₂ COOCH ₃ (hereinafter referred to as CVE), and the polymerization initiator 5.30 g of diisopropyl peroxydicarbonate was charged, and the internal pressure was adjusted to 0.1 MPa with nitrogen. The autoclave was heated to an internal temperature of 40 ° C. and stirred at 40 ° C. for 12 hours to conduct a polymerization reaction. After the stirring, unreacted CVE was distilled off to obtain 470 g of a precursor polymer polymerized by CVE. It was 5 * 10 < ³ > when the mass mean molecular weight of this precursor polymer was measured by GPC method.
Water was added to the obtained precursor polymer and the temperature was raised to 90 ° C., followed by stirring at 90 ° C. for 5 hours to hydrolyze a methyl ester group derived from CVE. Next, 10 g of acetic acid was added and the temperature was raised to 90 ° C., followed by stirring for 1 hour and adding water, whereby 95 mol% or more of the methyl ester groups of the precursor polymer were converted to —COOH. An aqueous solution of the water-soluble fluoropolymer (B1) was obtained. The non-volatile content concentration of the aqueous solution was 30% by mass.

Example 1
The aqueous solution of the water-soluble fluorine-containing polymer (B1) obtained in Production Example 1 is diluted with water, and the fluorine-containing surfactant (A11-1) represented by the following formula (III-1) is added and mixed. By doing so, a composition for antireflection coating was obtained. Table 1 shows the content (unit: mass%) of the water-soluble fluoropolymer (B1) and the content of the surfactant (A11-1) (unit: mass%) in the antireflection coating composition. .
CF ₃ CF ₂ OCF ₂ CF ₂ OCF ₂ COOH (III-1)

(Examples 2 to 4)
In Example 1, the content of the water-soluble fluoropolymer (B1) and the content of the fluorosurfactant (A11-1) in the antireflection coating composition were changed as shown in Table 1. Prepared an antireflective coating composition in the same manner as in Example 1.

(Comparative Example 1-1)
In Example 1, the composition for antireflection coating was carried out in the same manner as in Example 1 except that the fluorine-containing surfactant was changed to the fluorine-containing surfactant (A2-1) represented by the following formula (II-1). Was prepared.
CF ₃ (CF ₂ ) ₄ COOH (II-1)

(Comparative Examples 1-2 to 1-4)
In Comparative Example 1-1, the content of the water-soluble fluoropolymer (B1) and the content of the fluorosurfactant (A2-1) in the antireflection coating composition were changed as shown in Table 1. In the same manner as in Comparative Example 1-1, an antireflection coating composition was prepared.

(Comparative Example 1)
In Example 1, instead of the fluorine-containing surfactant (A11-1), a commercially available non-fluorinated surfactant, Nikkor SBL-2N-27 (product name, manufactured by Nikko Chemicals Co., Ltd.) was used. An antireflection coating composition was prepared in the same manner as in Example 1.
(Comparative Examples 2 to 4)
Reflection was carried out in the same manner as in Comparative Example 1 except that the content of the water-soluble fluoropolymer (B1) and the content of the non-fluorinated surfactant (Nikkor) were changed as shown in Table 1. A composition for prevention coating was prepared.

(Comparative Example 5)
In Example 3, an antireflection coating composition was prepared in the same manner as in Example 1 except that the fluorine-containing surfactant (A11-1) was not added.
(Comparative Examples 6-8)
In Examples 1, 3, and 4, in place of the fluorine-containing surfactant (A11-1), dodecylbenzenesulfone used in Examples 1 to 4 of JP-A-2004-37887 (Patent Document 7). The acid was used in the content shown in Table 1. Otherwise, the composition for antireflection coating was prepared in the same manner as in Examples 1, 3, and 4, respectively.

<Evaluation method>
(Evaluation of surface tension)
About the composition for antireflection coatings prepared in the above examples and comparative examples, the surface tension was measured with a surface tension meter ESB-V (product name, manufactured by Kyowa Chemical Co., Ltd.). The results are shown in Table 1.

(Evaluation of coating properties and refractive index)
The antireflection coating composition prepared in each of the above Examples and Comparative Examples was applied onto a silicon wafer using a spin coater, and then heated and dried at 120 ° C. for 90 seconds using a hot plate to form a film (antireflection film). ) The film thickness was about 100 nm when the content of the water-soluble fluoropolymer (B1) was 6% by mass, and about 40 nm when the content was 3% by mass.
The appearance of the obtained film was visually observed to evaluate whether a uniform film was formed. The results are shown in Table 1. When the surface tension of the coating solution is low and radial spin coating marks remain on the film, it is referred to as `` spin coating marks '', and when the surface tension of the coating liquid is high and a uniform film is not formed, "Sujimura".
The refractive index of the obtained film was measured using an ellipsometer. The refractive index was measured at 193 nm and 248 nm, which are exposure wavelengths generally used in the photolithography process. The results are shown in Table 1.
In general, the refractive index of the photoresist at the exposure wavelength is about 1.6 to 1.8, and if the refractive index of the antireflection film provided on the photoresist layer is less than that, a good antireflection function can be obtained. It is done.

From the result of Table 1, Examples 1-4 have surface tension reduced compared with the comparative example 5 which did not add surfactant, compared with the comparative examples 1-4 which added the conventional surfactant. However, the surface tension was effectively reduced by adding a smaller amount. The refractive indexes of the films in Examples 1 to 4 were almost the same as those in Comparative Example 5. From this, it can be seen that in Examples 1 to 4, the surface tension of the coating solution can be effectively reduced without deteriorating the refractive index of the film, thereby obtaining high coating performance. On the other hand, in Comparative Example 2 in which a large amount of a conventional surfactant (Nikkor) was added to such an extent that good coating performance was obtained, the film was not transparent and the refractive index could not be measured.
In addition, although an appropriate range of the surface tension of the coating solution depends on the coating method, with respect to the spin coating method, spin coating marks were generated in Example 1, and uneven stripes were generated in Comparative Example 1-4. It can be seen that the fluorine-containing surfactant (A) is preferably contained so that the surface tension of the composition for preventing coating is 13 to 35, preferably about 15 to 30.
Furthermore, in Comparative Examples 6 to 8 in which do not contain the fluorine-containing surfactant (A) and dodecylbenzenesulfonic acid is blended, the storage stability of the aqueous solution of the composition tends to be poor. In addition, “striped streaks *” in the film appearance evaluation of Comparative Example 8 was a level lower than the other examples although streaks were generated.

The composition for antireflection coating of the present invention is suitable as a coating solution for forming an antireflection film for photoresist. According to the present invention, without using PFOS and PFOA having 7 or more carbon atoms, which may be prohibited from the viewpoint of impact on the environment, the surface tension is low, the coatability is excellent, and the refractive index is low. An antireflective coating composition for a photoresist capable of forming an antireflective film is provided.

In addition, the entire contents of the specification, claims and abstract of Japanese Patent Application No. 2007-042418 filed on February 22, 2007 are incorporated herein as the disclosure of the specification of the present invention. It is.

Claims (8)

A fluorine-containing surfactant (A) containing the compound (A1) represented by the following general formula (I), a water-soluble polymer (B), and an aqueous medium (C) ,
The water-soluble polymer (B) contains 50% by mass or more of a water-soluble fluoropolymer (B1) having a polymerization unit (b1) represented by the following general formula (IV): Coating composition.
R ¹ —O— (R ² —O) _n —R ³ —X ¹ (I)
(In the formula, R ¹ represents a linear or branched perfluoroalkyl group in which the terminal fluorine atom may be substituted with a hydrogen atom or a chlorine atom, and R ² and R ³ are each independently Represents a chain or branched perfluoroalkylene group, the total number of carbon atoms of R ¹ , R ² and R ³ is 5 or less, n represents 0 or an integer of 1 or more, and X ¹ forms a salt. And —COOH or —C (CF ₂ Z ¹ ) (CF ₂ Z ² ) OH, each of Z ¹ and Z ² is a hydrogen atom, a fluorine atom, a chlorine atom or a trifluoromethyl group. )

Wherein Y ¹ and Y ² each independently represent a hydrogen atom, a fluorine atom or a chlorine atom, Y ³ represents a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group or a trifluoromethyl group, and Q represents an ether bond Or an ester bond, R ⁵ , R ⁶ and R ⁷ each independently represents a linear or branched perfluoroalkylene group having 6 or less carbon atoms, and X ³ may form a salt. A functional group having an acidic OH group, and a and b each independently represent 0 or an integer of 1 or more.) The composition for antireflection coating according to claim 1, wherein the fluorine-containing surfactant (A1) is a compound (A11) represented by the following general formula (III).
M ¹ CF ₂ CF ₂ O (CF ₂ CF ₂ O) _p CF ₂ COOA ¹ (III)
(In the formula, M ¹ represents a fluorine atom, a hydrogen atom or a chlorine atom, A ¹ represents a hydrogen atom, an alkali metal, NH ₄ , a monovalent group derived from an organic amine, or a quaternary ammonium group; Is 0 or 1.) The composition for antireflection coating according to claim 1 or 2 , further comprising an organic amine (D). The content ratio of a fluorine-containing surfactant (A) is 0.001-10 mass%, The composition for antireflection coating as described in any one of Claims 1-3 . The composition for antireflection coating according to any one of claims 1 to 4 , wherein the content of the water-soluble polymer (B) is 0.1 to 20% by mass. The composition for antireflection coating according to any one of claims 1 to 5 , wherein the content ratio of the aqueous medium (C) is 70 to 99.9 mass%. The composition for antireflection coating according to any one of claims 1 to 6 , wherein the water-soluble polymer (B) has a mass average molecular weight (PMMA conversion by gel permeation chromatography method) of 1000 or more and 50000 or less.   Antireflection as described in any one of Claims 1-7 whose ratio for which a polymerization unit (b1) accounts among all the polymerization units which comprise the said water-soluble fluoropolymer (B1) is 20 mol% or more. Coating composition.